Not all vintage razors of the same model are created equal. Some seem to shave better than others.
I have a theory that the best vintage razors are those that have seen a lot of love back in the day. In other words, the more worn and well-used a razor is, the more likely it is to be a great example of that particular model. People hang on to what works well and shove the other stuff in a drawer (with the case, shipper, and instructions). The pristine examples then get sold on eBay decades later for hundreds of dollars. The user-grade razors just keep delivering great shave after great shave.
Is this theory illogical lunacy? You tell me!